This paper discusses a criterion judging whether a walking plan will be completely done or not, considering dynamics. A conventional“Zero Moment Point”is a useful criterion, but it is available for only a walk on a flat even terrain, and not available for that on a general rough terrain. So, we propose a new criterion named“Tumble Stability, ”in which considering a direction that a machine would be tumbling, if all the contact points except two were disappeared. The tumbling motion will be protected in practice, if some imaginarily disappeared contact points can produce a supporting force to avoid tumbling. In a case that no contact points can produce a force against tumbling, the machine will tumble indeed. By using this criterion, we can judge a plan of walking on any terrain, including walls and ceilings. We also propose a value indicating a stability named“Tumble Stability Margin, ”which equals to the conventional“Stability margin”in case of walking on a flat even terrain, and is useful for any other general terrain.
This paper presents a new computationally efficient method for calculating steering control commands for the articulated body mobile robot “Koryu-II (KR-II) ”. KR-II is composed of six cylindrical segments linked in series and has a long snake-like appearance. The introduced method considers that each segment center travels over a given desired trajectory, so that, knowing the position of the foremost segment, the position of the following segments can be calculated using geometrical relationships, and therefore the bending angle Bsey of these segments, which are to be controlled, can be derived. This method is based on a trajectory planning scheme in the inertial reference frame, and tracks the segment center positions using a simple and effective numerical searching algorithm, making it feasible for real time computation. The extension of this method for the “W-Shaped Configuration” (a configuration that augments the lateral stability of the robot) steering control is also addressed, and the validity of these methods is verified by experiments on the mechanical model KR-II.
Recognition of the actual position is very important for a mobile robot to move around in its environment. The most common method for position estimation is dead reckoning, usually achieved by integrating wheel rotation along the path. This method, however, has a serious problem. It is difficult to determine the parameters such as effective wheel diameter, distance between wheels, and slip factors with sufficient accuracy. This makes the error of position estimation larger. In this paper we propose the utilization of an optical fiber gyroscope (OFG), in combination with the information provided by the wheel encoders to improve the accuracy of position estimation. The formulation using Kalman filter to combine information of encoders with that of OFG is described. The simulation and experimental results show the effectiveness of the proposed method.
There are various types of visual sensors. When we try to use only one of them as a sensor of an autonomous robot, it may be difficult or take a long time to obtain required information. In such a case, it is useful to use heterogeneous visual sensors whose features are different. Furthermore, we can improve the efficiency not only by fusing data gotten by each sensor but also by modifying the behavior of each using information from others. We fabricated an active vision system that consists of a range finder and a monocular camera system as a sensor system which combines heterogeneous visual sensors. As an example, we applied it to a parts-picking problem.
In this paper, the authors introduce a biped walking control method for adapting to an unknown uneven surface, and a biped walking robot which has a special foot mechanism for the control method. The biped walking robot has an ability to acquire, during its dynamic walking, the information of the landing surface's height and angle of inclination. The authors performed adaptive walking experiments with the robot using the control method. As a result, dynamic biped walking adapting to an unknown uneven surface was realized. The adaptable uneven surface's height range per one step walking was from -16 to +16 [mm], and the adaptable angle of inclination range was from -3 to +3° at the maximum walking speed of 1.28 [sec] per step with a 0.3 [m] step length.
In this paper, an optimization algorithm by the complex method is proposed to solve the two-point boundary value variational problems with or without some constraints. The optimum solution of the variational problem is derived as a finite set of the control points of uniform B-spline. The algorithm is very simple and easily applicable to the trajectory planning of manipulators with redundant degrees of freedom under the conditions that the end effector path is specified and the smoothness of the trajectories or the constraints of the joint torques are simultaneously considered. By comparing the calculation results, it is clear that the complex method is more effective than the gradient method, which was proposed earlier by the authors, because the former can obtain the trajectories with a better performance index particularly in the case the trajectories need to satisfy the strict constraints but the latter can not.
This paper proposes a novel teleoperation system for multi-micro mobile robots. The system issues teleoperation commands by recognizing such operator's intuitive behaviors as the operator wants to move multiple robots simultane-ously or to move single robot incrementally through operator's object gathering behavior with hand or object sliding behavior with fingers respectively. It also controls the zoom ratio and viewing angle of camera by recognizing the operator's intuitive behaviors to monitor the robots closely from different view angle through the operator's head motion towards the monitor display. Utilization of operator's behavior in accordance with instinctive behavior framework of small objects handling realizes intuitive teleoperation system for multiple micro mobile robots. The effectiveness of the system is confirmed by teleoperation experiments of multiple 1 [cm3] cubic mobile robots driven by PZT-actuators.
In vision-guided robotic operations, vision is used for extracting necessary information for achieving the task. Since visual recognition is usually performed with limited resources, visual sensing strategies should be planned so that only necessary information is obtained efficiently. This paper describes a method of generating visual sensing strategies for assembly tasks based on knowledge of the task to be performed. The generation of the appropriate visual sensing strategy entails knowing what information to extract, where to get it and how to get it. This is facilitated by the knowledge of the task, which describes what objects are involved in the operation, and how they are assembled. In the proposed method, using the task analysis based on face contact relations between objects, necessary information for the current operation is first extracted. Then, visual features to be observed are determined using the knowledge of the sensor, which describes the relationship between a visual feature and information to be obtained. Finally, feasible sensing strategies are evaluated based on the predicted success probability, and the best one is selected. Our method has been implemented using a laser range finder as the sensor. Experimental results show the feasibility of the method, and point out the importance of task-oriented evaluation of sensing strategies.
This work presents a new theoretical approach to hybrid position/force control. It develops a method for the design of controllers of constrained manipulators. In this work also the robustness considerations are given. It can be shown that the proposed control system has robustness properties for a class of dynamic uncertainties. In order to improve the robustness property integral controller is applied to the force control loop. The usefulness of this hybrid control system is demonstrated through simulations of a constrained two degrees of freedom robot manipulator. Finally this control system is applied to grinding machining. Grinding is very important industrial work. However, it is also very difficult work for robot manipulators. 2 degees of freedom DD-manipulator is used for this machining. Performances of this machining demonstrate the usef ullness of the proposed control system.
We believe that personal robots like current personal computers will be used in an office and at home in the near future. And we have already designed function-classified parallel computer architecture for personal robots: ASPIRE (ASynchronous, Parallel, Interrupt-based, and REsponsive architecture) . In this paper, we design and implement the personal robot ASPIRE-II based on ASPIRE using RISC processors. Many researchers think that RISC processers are not suitable for embedded application due to the pipeline hazards, and the loads and stores of a large number of registers in case of interrupts. However we dare to apply RISC prosessers (SPARC family) to ASPIRE so as to have both high computing performance and good interrupt capability. Definitely, we apply register windows of SPARC architecture to ASPIRE. We also describe the efficiency of the architecture by evaluating ASPIRE-II.
The nonholonomic systems considered in robotics are mechanical systems with nonintegrable constraints. These systems have the property that the dimension of the reachable space is larger than the number of degree-of-freedom. A two-joint planar manipulator with the second joint free is one of such systems. Chaos, on the other hand, is another major topic in nonlinear dynamics and has the property that a dynamical system is sensitive in the initial conditions. The two phenomena have the same mathematical background from integrability point of view. In this paper, we study when and how the manipulator exhibits the chaotic behavior. We propose a control strategy for simultaneous positioning of the two joints, based on the analysis of nonlinear behavior. Its effectiveness is to be shown by experiments.